Astroparticle Physics Forum COSMOVIA

VIA lecture by Dr. C.Corral "Axions in gravity with torsion" was given on 23.10.2015. The pdf file of the presentation is attached and the record of his VIA lecture is in VIA library
http://viavca.in2p3.fr/cristobal_corral.html
The following questions and comments were made in discussion:
Shantanu: Can I ask a pedantic question?
Einstein-Cartan theory is also sometimes called Einstein-Cartan-Sciama Kibble theory of gravity. I presume you mean the same theory, right? Or is there any subtle difference between your formalism and Einstein-Cartan-Sciama-Kibble gravity?
Shantanu: does the model by Lattanzi and Mercuri have isocurvature fluctuations?
hantanu: Just a comment. One of the persons on the chat Dr. Poplawski has pointed out that einstein-Cartan theory is incompatible with extra dimensions (He can correct me of course if I misquoted him in any way)
You are welcome to continue discussion in replies to this post!

First of all, I would like to appreciate the interest and the attendance in the presentation about "Axions in gravity with torsion". In order to continue with the discussion, I will answer the questions for which I know the answers, even though some of them were already discussed within the talk.

Prof. Shantanu, as I mentioned before, you are right. The Einstein-Cartan theory, which was the main framework considered here, is actually the so-called Einstein-Cartan-Sciama-Kibble theory. Thus, your assumption was right and my apologies for omission of the last two authors, whom certainly recovered the Riemann-Cartan geometry in the study of gauge theories of gravitation.

The way that Lattanzi and Mercuri obtained the limits on the tensor-to-scalar ratio was by means of the isocurvature perturbations. I am attaching here the reference if you are interested on the details: http://arxiv.org/abs/0911.2698

Regarding your last question, I am not aware about the incompatibility of extra-dimensions with the Einstein-Cartan theory. I will check the reference you mentioned in the talk and it would be worth whether Prof. Poplawski can give us more details about his arXiv article. However, in the present work it was proposed a 4-dimensional scenario for the torsion-descended axions and thus, there is no problem with your concern. My argument about the scale of gravity in the slide 18 was in order to have an idea of what would happen if the scale of gravitation were different from the one in four dimensions. Certainly, a detailed discussion deserves a deeper study about this point.

Best regards,
Cristóbal.

Dear Cristobal,
Thank you for a nice talk.
Prof. Poplawski's paper is http://arxiv.org/abs/1001.4324.He can provide more details or conversely you can
let him know if you disagree with any of his points (as presumably that's the goal of forums like VIA)